Securing our nation's borders against illegal entrants has become the most reverberant, and often most polarizing, rallying cry of the nation's recent political discourse. But a different kind of illegal threat entering this country every day is at least as present on the minds of law enforcement officials across America: the constant flow of dangerous, cheap synthetic drugs through the mail.

Last month, a bipartisan group of five U.S. Senators held a roundtable forum at the U.S. Capitol to discuss the biggest threat to public safety most Americans have never heard of. The Senators questioned a panel of government experts, including representatives of the U.S. Postal Service, Customs and Border Protection; Drug Enforcement Agency; and Department of State, who acknowledged the crisis. Each emphasized its causes as systemic, making any fast solution unlikely.

There was also agreement that there is far less risk from packages entering the country via express delivery companies, which are more likely to go through customs screening and, if necessary, physical inspection.

While these systemic failures may be unknown to most of us, the dangers of these synthetic drugs and their strain on police departments has become a daily reality for a growing number of communities.

Much of the panel's discussion centered on the powerful synthetic opiate Fentanyl, the latest scourge responsible for thousands of drug deaths across the United States last year. Whether in pill or powdered form, or mixed with heroin, the drug is a killer. Sen. Ron Johnson, the Wisconsin Republican who chairs the Senate Homeland Security and Government Affairs Committee, noted that Fentanyl was the cause of 30 deaths in Milwaukee alone since December.

Fentanyl is just the most recent center of a growing synthetic drug epidemic — drugs with street names like bath salts, K2, Flakka and Spice have already been the identified cause of overdose deaths in many states. They are inexpensively produced, mostly in China and India, and shipped directly into the United States. Senators at the roundtable even discussed documented cases in which the drugs were mailed into the United States to be smuggled into Mexico, where they were mixed with heroin and smuggled back across the border for sale on the street.

Because the drugs are sold cheaply, they are hard for police to control. Constantly-changing chemical compounds not only make them expensive for police labs to test for, but challenging for state laws to keep up with. If a new compound is not yet defined as illegal, courts may not see them as a violation of parole or treatment terms, compounding the challenge for local police agencies to enforce. They need assistance addressing supply, as international drug dealers increasingly rely on mail delivery.

With 275 million packages entering the U.S. last year through international mail and express delivery companies, physically inspecting every one is not realistic. Some strategic screening upon entry is essential.

The government experts at last month's Senate hearing made clear that information about the sender and package contents, received electronically and in advance of the shipment, is essential to this screening. It allows federal officials to strategically target packages for inspection, which according to customs makes their security much more effective. In fact, 47 U.S. agencies depend on this data to perform their enforcement duties.

But packages entering from foreign posts almost never submit advance data. As a result, they very rarely get inspected at all. By contrast, all packages (98 percent) entering the U.S. by commercial express carriers are required to submit Air Cargo Advance Screening data, and do. Customs and Border Protection maintains different rules and regulations for packages entering from foreign national postal operators than it does for commercial operators.

International mail is governed by a U.N. specialized agency called the Universal Postal Union, in which the United States, as a member, gets one vote in all decisions. Despite the efforts of the U.S. and allies, the agency is not expected to require postal operators to provide advance data (or collect it from shippers in the first place) any time soon. This probably means we shouldn't expect much useful help from beyond our borders soon, either.

For police departments operating under strain around the country, this will not come as good news. Until these systemic failings can be fixed, bolstering drug education may be their most promising strategy.

Don Soifer is executive vice president of the Lexington Institute think tank in Arlington, Va, and serves on the serve on the Department of State Advisory Commission on International Postal and Delivery Services as well as on the District of Columbia Synthetic Drugs Task Force. His email is soifer@lexingtoninstitute.org.